Not Applicable
Not Applicable
This invention relates to an apparatus for the manufacture of compacts, preferably a tabletting machine.
When compacts of any types are manufactured and, specifically, when tablets are made the proportioning of the materials fed, i.e. the substance to be compacted, is of a particular significance, especially when high-performance presses are used. In the state of the art, such high-performance presses substantially comprise a rotary cavity block table and a stationary filling shoe associated therewith for feeding the material used which is to be compacted in the cavity block.
While accuracy of proportioning can be ensured by the use of modifiable stirring blade shoes even if performances are high the consequence of the charging principle, which is characterized by a combination of the stationary filling shoe above the rotary cavity block table, is that relatively large material losses have to be tolerated. As a rule, a sealing strip is provided between the filling shoe and the cavity block table. If the filling shoe is not exactly adjusted metallic abrasion might occur on the filling shoe sealing strips. Abraded metallic particles might migrate into the product to be manufactured, which causes the so-called black spots to form.
Attempts have been made in the past to overcome this problem by adjusting the distance between the filling shoe and the cavity block table as precisely as possible prior to putting them into operation. What matters here is the skillfulness of the person setting the machine in reducing the loss of material to an optimum extent while minimizing abrasion on the sealing strips at the same time. Once manufacture is under way it is no longer possible to carry out product-related corrections to the setting.
It is the object of the invention to remedy the aforementioned nuisance. In particular, further improvements are intended to be made to proportioning and the occurrence of black spots on the surface of the compact or tablet is intended to be minimized.
According to the invention, an apparatus for the manufacture of compacts and, specifically, tablets provides that the filling shoe is supported so as to be adjustable in height with respect to the surface of the rotary cavity block table via a servomotor. This makes it possible to optimally adjust the distance between the filling shoe bottom plate and the cavity block table by an extremely precise adjustment, which may be in the range of some 100ths of a millimeter, to such a degree that the loss of material may be individually minimized depending on the composition and grain size of the material to be compacted with the distance, on the other hand, being selectable so that no abrasion will occur on the sealing strips and, therefore, the black spots requiring to be avoided will not form.
Accordingly, the bottom plate of the filling shoe may be mounted on a base which is adjustable in height via a motor disposed in the main frame of the machine. In addition, a measuring device may be provided via which the distance between the bottom plate of the filling shoe and the surface of the rotary cavity block table is measured. This permits to monitor the settings tailored to product quality, on one hand, and to acquire them in a reproducible manner, on the other. An output device for the values measured, in particular, may serve this purpose.
In order to ensure a constancy of the optimized gap distance, the gap width may also be ensured by means of a control circuit in which the gap with is adjustable as a controlled variable even if differences in height occur during the rotational motion of the rotary cavity block disk.